Surface modification and structure constructing for improving the lithium ion transport properties of PVDF based solid electrolytes

Solid electrolytes have attracted much attention for their potential application in next generation lithium ion batteries with high energy density and safety. Especially, solid polymer electrolytes have become a research focus for the advantages of flexibility, easy-prepare and low cost. However, low ionic conductivity at room temperature hinders their development. Here, two strategies are designed to improve the lithium ion transport properties of PVDF based solid electrolytes. The first, a composite solid electrolyte with Nickel Oxalate modifying the surface morphology of PVDF is designed and shows excellent impedance performance and perfect lithium ion transference performance. The results show that the dense surface of the PVDF based solid polymer electrolytes is conducive to the transmission of lithium ions. The second, a composite polymer solid electrolyte composed of ZIF-8 and polyvinylidene fluoride is designed and prepared, the obtained solid electrolyte shows high lithium transference number of 0.833 and lithium ion conductivity of 1.5 × 10-4 S/cm at room temperature. The research results indicate that the dodecahedron structure of ZIF-8 provides a stable channel for lithium ion transmission in the PVDF based solid electrolyte material. The LiFePO4/Lithium cells with two kinds of improved composite solid electrolyte show satisfactory rate performance and cycle stability at room temperature.